Constant tension drive



y 1944- E. .1. OTTO CONSTANT TENSION DRIVE 4 Sheets-Sheet 1 OriginalFiled May 8. 1940 VIII.

May 2, 1944. E, OTTO 2,348,090

CONSTANT TENSION DRIVE Original Filed May 8, 1940 4 Sheets-Sheet 2 Ca AWWW

I y 1944. E. J. OTTO CONSTANT TENSION DRIVE 4 Sheets-Sheec 3 OriginalFiled May 8 1940 May 2, 1944. E. J. OTTO CONSTANT TENSION DRIVE 1940 4Sheets-Sheet 4 Original Filed May 8 Patented May 2, 1944 CONSTANTTENSION DRIVE Eugene J. Otto, Milwaukee, Wis., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis., a corporation ofDelaware Original application May 8, 1940, Serial No. 333,897, nowPatent No. 2,346,047, dated April Divided and this application October10, 1941, Serial No. 414,400

'7 9 Claims.

This invention relates to a transmission element which is of specialutility in constant tension drives.

This application is a division of application S. N. 333,897, filed May8, 1940.

In the treatment of continuous sheet, wire etc. material, it is often ofthe utmost importance to maintain a constant tension on the strip ofmaterial being wound or unwound, or in course of treatment. While manysystems are known for obtaining constant tension under suchcircumstances, the present invention provides a drive of greatsimplicity and accuracy, and one which does not involve great expense.

It'is an object of this invention to provide a power transmissionelement mounted on a shaft for limited angular movement thereon, withresilient means between said power transmitting element and its shaft,whereby the angular position of said power transmitting element on itsshaft depends upon the torque transmitted by said transmission element.

A further object of this invention is to provide a sheave mounted forlimited angular movement on a shaft, with spring means for biasing saidsheave in one direction, a switch carried by said shaft, and means forclosing said switch-upon predetermined angular movement of said sheaveon its shaft against the influence of said spring.

A further object of this invention is to provide means for adjusting thespacing between said switch contacts, which may be adjustable while theshaft is rotating.

A further object is to provide, in the mechanism recited aboveraplurality of switches adapt- Fig. 9 is a sectional view taken on lineIXIX of Fig. 8;

Fig. is a detail view, partly in section, taken on line XX of Fig. 8;and

ed to be closed at various relative angular positions of said shaft andsheave.

Other objects will become sapparent fromthe following detaileddescription, taken in conjunc- Lion with the drawings, in-which:

Fig. 1 is a diagrammatic showing of a con* stant tension drive inaccordance with this invention;

Fig. 2 is an elevation, partly in section, of a shaft and sheaveillustrating a detail of the drive;

Fig. 3 is a sectional view taken on line III-III of Fig. 2;

Fig. 4 is a view similar to Fig. 2, but illustrating a modification;

Fig. 5 is a sectional view taken on line VV of Fig. 4;

Figs. 6 and-7 are fragmental views illustrating details of circuit,connections of the modiflcation shown in Figs. 4 and 5;

Fig. 8 is an elevation, partly in section, of a shaft and sheave similarto Fig. 2, but illustrating a modification in which the spacing betweenswitch contacts is adjustable during rotation of the shaft;-

- a higher motor torque.

Fig. 11 is a diagrammatic view showing a modification of the driveillustrated in Fig. 1.

While the drive of this invention is applicable to winding rolls,unwinding rolls, or intermediate rolls, it is shown in Fig. 1 as beingapplied to a winding roll I5, on which is wound the material to betensioned, which is shown as a strip of brass or the like I6. Roll I5 isdriven from output shaft H of speed changer I8, as by means of sheavesI9, 20 and belts 2|. Constant speed motor 23, energized from a powersource 24, is connected to drive input shaft 26 of speed changer I8through sheave 21 on motor shaft 28, V-belts 29, and sheave 30 on shaft26. Speed changer I8 in this instance comprises input shaft 26 andoutput shaft II connected by a plurality of V-belts 32 connectingadjustable diameter sheaves 33 and 34. These sheaves comprise aplurality of conical disks adjustably spaced so that the relativespacing between cooperative disks determines the effective pitchdiameter of each sheave. A pilot motor 36 drives worm actuator 31 whichdetermines the relative spacing of the disksof sheaves 33 and 34, beingarranged to increase the effective diameter of one sheave whiledecreasing the diameter of the other. In this way, energization of motor36 alters the speed ratio of the input and output shafts 26, ll of speedchanger I8. Pilot motor 36 is energized from source 24 through a switch40 carried on sheave 30, the contacts of said switch being connected tocollector rings 38, 39 which are in contact with brushes 4|, 42,respectively. I

The details of the construction of speed changer I8 form no part of thepresent invention, and need not be described herein. A detaileddescription of the speed changer may be found in Patent No. 2,221,166issued to Casper W. Heinrich and Eugene J. Otto on November 12, 1940.While this particular speed changer is described herein for purposes ofillustration, it is clear that any other known type of speed changer maybe substituted therefor.

With motor 36 normally deenergized, constant speed motor' 23 normallydrives winding roll l5 at a constant speed through speed changer I8. Asthe strip I6 builds up on roll I5, its effective diameter increases, andthe material I6 is wound on roll I5 at a faster rate. This tends toincrease the tension on strip I6, and the work' done by motor 23increases.

Since the speed of the motor is substantially constant, the increasedwork done by the motor is reflected in As described below, this increasein. torque is utilized to energize pilot motor 38 to reduce the speed ofoutput shaft IT, thereby reducing the speed of rotation of .roll l5,until equilibrium is reestablished. This reduction in the speed of rollI! is repeated from time to time, until the winding step is completed.

Means for closing switch II in response to a change in torque on themotor drive is best shown in Figs. 2 and 3. This torque-responsiveswitch'rnay be carried by either constant speed motor shaft 2. orconstant speed input shaft 26 of the speed changer. As shown in Figs. 2and 3, input shaft 28 carries fixed thereon a sleeve 43 provided withspring arm 44 and switch arm 45. Spring arm 44 has a spring seat 41 nearthe end thereof, and also carries an adjustable stop screw 48 retainedin any desired position by lock nut 49.

Switch arm .45 carries a plunger SI for actuating switch 40. Plunger IIis slidably retained in the bore of plunger housing 52, and is biased tothe right as seen in Fig. 2 .by a spring 54 backed by plunger guide 3!,the latter being retained by lock nut 53'. Housing 52 is threaded in atapped bore in switch arm-45, and is retained by means of lock nut 58.

V-belt sheave I is freely mounted on sleeve 43 for limited angularmovement with respect to shaft 26. The sheave is provided with aninternal lug or abutment ll which is provided with a spring seat BIwhich cooperates with spring seat 41 to support a helical compressionspring 59. A bolt 6| passes through spring arm 44, helical spring 59,and lug 51, being suitably retained at both ends to provide for the maximum desired spacing between arm 44 and lug II. The minimum spacingbetween arm I4 and lug I1 is determinedby the setting of stop screw IIwhich cooperates with lugll to prevent too great a degree of movementbetween shaft 28 and sheave 30 after switch 40 has been closed.

Inward of its outer flange, sheave 30 carries a lug or bracket .2 whichsupports insulated switch 40, which is normally open but may be closedby a slight pressure on switch button 63. Leads 04 and Cl electricallyconnect the switch contacts (not shown) with collector rings 38 and 39,respectively, which are suitably supported on and insulated from sleeve43. Brushes ll and 4! connect with rings II and I9, respectively, toclose the circuit to pilot motor It through switch ll.

The normal position ofsheave 30 on shaft 26 is shown in Fig. 2. It isassumed that sheave ll drives shaft ll in a clockwise direction, as seenin Fig. 2. When the torque on shaft 26 exceeds a predetermined amount,sheave It moves clockwise with respect to shaft 26 against the pressureof spring It. A predetermined degree of such relative movement resultsin engagement between plunger BI and switch button I! to close switchII. The amount of movement necessary to actuate switch button 01 may bedetermined by anal adjustment of plunger housing II in arm ll. Aspointed out above, the

extent of relative angular movement between sheave II and shaft islimited by stop screw ll.

Closing of switch ll energizes pilot motor 86 to reduce the speed ofoutput shaft ll of the again; This operation is repeated a number oftimes during the winding operation, maintaining a substantially constanttension on strip 16.

While the construction of Figs. 2 and 3 has been described withreference to a winding roll, it will be understood that, by locatingswitch 40 on the opposite side of switch operating arm 45, and modifyingthe connections to pilot motor II to operate in the reverse directionupon closing switch 40, constant tension on an unwinding roll may beprovided by repeatedly speeding up output shaft II as the strip l8unwinds from roll II,

One arrangement of'this type is illustrated in Figs. 4-7, whichillustrate a construction which may be utilized on a winding roll, anunwinding roll, or an intermediate roll, to maintain substantiallyconstant tension thereon. As before, speed changer input shaft 28carries sheave ll, freely mounted for limited angular movement withrespect to the shaft. Sleeve 43 is fixedly mounted on shaft 28 andcarries spring arm 44 and switch actuating arm 45. As in themodification of Fig. 2, compression spring 59 is mounted between sheavelug 51 and shaft arm 44, the maximum extension of the spring beingdetermined by the setting of bolt 6!, and the maximum compression of thespring being determined by the setting of stop screw 48.

In the modification of Fig. 4, however, two switches 40 and 40' areprovided, one on each side of switch, arm 45. These switches aresupported on sheave It by means of brackets or lugs 82, 62',respectively. In each case, the switch is operable by contact of plunger5|, 5| with switch button 83 or 63', plungers 5|, 5| being adjustablycarried by arm 45 as previously described. One contact from each switchis con nected by leads I, 84' with collector ring 38 (see Fig. 6); theother contact of switch M is connected to collector ring 39 by means oflead 65; while the remaining contact of switch 40' is connected tocollector ring I! by means of lead 65' (see Fig. 7). Current is takenfrom collector rings II, I. and 8! by means of brushes 42', ii and 42,respectively, and connections are made from brushes 42', II and 42 insuch manner (not shown) that when switch I is closed the pilot motorwill be energized in one direction (to increase the speed of outputshaft ll); when switch II is closed. the pilot motor will be energizedin the opposite direction (to increase the speed of output shaft l1);and when both switches are open, the pilot motor is deenergized, and thespeed ratio of speed changer It remains constant. Since such motorconnections are well known and form no part of the present invention,they are not illustrated herein.

It will be understood that spring 50 is adjusted so that, at apredetermined desired tension, switch operating arm ll will bemaintained at the neutral position shown in Fig. 4, pilot motor 30 beingdeenergized. If the tension increases, assuming shaft 28 is driven bysheave III in a counterclockwise direction as "seen in Fig. 4, sheave IIwill move slightly in a counterclockdirection with respect to shaft 2.against the tion with respect to shaft 26 under the influence of spring59, to close switch 40. This would energize pilot motor 38 to operate ina direction to change the speed ratio of speed changer I8 to increasethe tension on strip l6. Therefore the arrangement of Figs. 4-7 isapplicable to winding rolls, unwinding rolls, or intermediate rolls of astrip mill.

The above modifications of the invention provide a tension responsiveswitch which operates satisfactorily where a predetermined, constanttension is desired. The degree of tension required to actuate the switchmay be adjusted either by changing the preset compression of spring 58or by axial movement of hollow screw or plunger casing 52 or -52, whichchanges the extent of relative angular movement of sheave 30 required toactuate switch 40 or 40'. 8 But in order to effectuate either of thesechanges, it is necessary to stop the drive. Sometimes it is desired toalter the tension of the strip while the drive is in operation. For thispurpose the modification illustrated in Figs. 8, 9 and 10 has beenprovided.

In this modification, sheave 30 is mounted for limited angularmovementwith respect to shaft 26, as before, with compression spring 59carried between the sheave and shaft arm 44. Shaft arm 45 carries aslidable plunger case 81 which is biased to the right (Fig. 8) bycompression spring 68. Plunger is carried in plunger casing 81, and isbiased to the left by spring 54, which is retained between a flange onplunger' 5| and plunger guide 53. The extending end of plunger 5| abutsa bell crank lever 69 which is urgedtoward plunger 5| by spring 10.Switch button 83 is located within spring I0 and is adapted to beactuated by counterclockwise movement of hell crank lever 69, Fig. 10.

Plunger carrier 61 is slidably supported in a guide in arm 45 and isbiased to the left under the action of spring 88, as seen in Fig. 8. Theaxial position of plunger carrier 81 is determined by a cam 12. As shownin Fig. 10, cam I2 is inclined with respect to the axis of plunger case61, and movement of cam I2 axially of shaft-26 determines the initialaxial position of plunger case 61, thereby determining the extent ofrelative angular movement between shaft 28 and sheave 30 required toactuate switch 48.

Cam I2 is supported on a disk I3 which is: supported at one end ofsleeve 43 for limited movement axially of said sleeve. The reduced end14 of the hub of disk I3 carries a frictionless thrust bearing I5.Handwheel I6 is fixed to the outer race of bearing I5, and is threadedat 11 to cooperate with the threaded portion of hollow actuating screwI9, the inner end of which is fixedly supported in the inner race offrictionless bearing 80, the outer race of which is fixedly mounted inthe end of sleeve 43. Actuating knob 82 is connected with a plunger 83which is biased inward by means of spring 84. As indicated at 85,plunger 83 is splined in actuating screw I9, permitting axial movementbetween plunger 83 and actuating screw I9, but preventing rotarymovement therebetween. A clutch 86 is provided between knob 82 andhandwheel I6.

Normally knob 82 and handwheel I6 are clutched together due to theaction of spring 84 on plunger 83. During rotation of shaft 26 andsheave 30, knob 82 and handwheel I6 and the parts connected thereto maybe stationary, or may rotate with the shaft and sheave. If it be desiredto move cam I2 to change the setting of switch operating plunger casing61, handwheel have been illustrated and described, it will be ment beingtransmitted to actuating screw I9 through splined plunger 83. Actuatingscrew 19 being retained against axial movement by fric-' tionless thrustbearing 80, rotation of actuating screw I8 results in axial movement ofhandwheel IS, the hub of which is in threaded engagement 1 with actuatorscrew I8. Axial movement of handwheel I6 is transmitted to disk "I3through thrust bearing I5, thereby causing axial movement of cam I2which determinesthe position of plunger casing 61. It is clear from theabove description that the modification illustrated in Figs. 8, 9 and 10provides means for determining and changing, while the drive isinoperation, the amount of angular movement between sheave 30 and shaft26 required to close switch 40.

While the description herein refers to a V-belt sheave 30, it is clearthat it would be within the scope of this invention to utilize a flatbelt pulley, a gear, or other mechanical power transmitting element onshaft 26 in lieu of sheave 30, and the word pulleyflas used in theclaims is intended to include such power transmitting elements.Furthermore, while the description relates to the spring biased sheavebeing mounted on speed changer input shaft 26, it could equally well bemounted on motor shaft 28 or any shaft intermediate these. Obviously,the spring biased sheave maybe utilized anywhere on the input side ofthe speed changer. The spring-biased sheave is also obviously applicableto other types of drives, whether used to maintain constant tension orfor other purposes.

A further modified construction in accordance with this invention isillustrated in Fig. 11, wherein a motor 23, energized from power source24, drives winding roll I5 through a speed changer l8. The latter isadapted to have its speed ratio between input shaft 26 and output shaftII changed by means of pilot motor 36. Pilot motor 36 is energized bynormally open, switch 88 operable by current responsive relay 89, whichcan be adjusted to operate at any desired current by means of adjustablerheostat or other impedance 90.

If, during the winding operation, tension on strip I5 increases, thetorque on motor 23 will increase and motor 23 will draw a heaviercurrent from line 24. Upon a predetermined increase of current to motor23, current responsive relay 89 will close switch 88 energizing pilotmotor 36 to reduce the speed of output shaft l1 and roll l5. When thespeed of roll l5 has been reduced sufliciently to restore the tension onstrip Hi to a desired value, the torque on motor 23 will return tonormal, the current taken by motor 23 will return to normal, relay 89will open switch 88, and pilot motor 36 will be deenergized until thetension should again increase.

While specific modifications of the invention understood thatmodifications and equivalents such as readily occur to those skilled inthe art are included Within the scope of this invention which isintended to be limited only by the scope of the claims appended hereto.

It is claimed and desired to secure by Letters Patent:

1. Power transmitting mechanism comprising a pulley provided with aninternal abutment and freely mounted on a shaft for limited angularmovement with respect thereto, said shaft being provided with anabutment fixed thereto within said pulley, and a compression springretained between said abutments, said spring being of such stiffness asto transmit the normal load torque of said mechanism and to yield whensaid mechanism is subjected to higher than normal torque, an electricalswitch carried by said pulley and provided with an actuator, and acooperating abutment carried by said shaft in position to contact saidactuator to close said switch upon relative angular movement of saidpulley and said shaft.

2. Power transmitting mechanism comprising a rotatable shaft, a powertransmitting element mounted on said shaft for limited angular movementwith respect thereto, resilient means interposed between said powertransmitting element and said shaft, said resilient means havingsufficient stiffness to transmit the normal load torque of saidmechanism between said shaft and said element and to yield upon theoccurrence of a torque greater than normal, switch actuating meanscarried by said shaft, and a switch carried by said transmitting elementon 7 each side of said switch actuating means in position to be actuatedthereby upon predetermined angular movement in either direction ofrotation of said transmitting element relative to said shaft.

3. Power transmitting mechanism comprising a rotatable shaft, a pulleymounted on said shaft for limited rotary movement relative thereto,'an

electrical switch carried by said pulley, a coin claim 3 wherein saidcam moving means com-' prises a threaded member rotatably mounted onsaid shaft and axially fixed with respect thereto, a cam carrying membersplined on said shaft, and an adjusting member axially fixed withrespect to said cam carrying member and rotatable with respect thereto,said adjusting member being threadably engaged with said threadedmember. I

5. Power transmitting mechanism as defined in claim 3 wherein said cammoving means comprises a threaded member rotatably mounted on said shaftand axially fixed with respect thereto, a cam carrying member splined onsaid shaft, an adjusting member axially fixed with respect to said camcarrying member and rotatable with respect thereto, said adjustingmember being threadably engaged with said threaded member, and resilientmeans for clutching said threaded member to said cam adjusting memberagainst relative rotary movement therebetween.

8. A power transmitting mechanism comprising a rotatable powertransmitting element, a second rotatable power transmitting elementarranged'for limited angular movement with respect to said first powertransmitting element,

- a switch carried by one of said elements, and

means responsive to a change in torque transmitted by said mechanism foractuating said switch, said means being arranged to transmit the normalload torque from one to the other of said elements.

7. A power transmitting mechanism comprising a rotatable shaft, a pulleymounted on said shaft for limited rotary movement relative thereto, aspring biasing said pulley in one angular direction on said shaft, saidspring being of sufficient stillness to transmit the normal load torqueof said mechanism without substantial yielding and to yield upon theoccurrence of a torque greater than normal, an electrical switch carriedby said pulley, a cooperating switch actuator carried. by said shaft inposition to actuate said switch upon predetermined relative rotarymovement between said pulley and said shaft; and means for adjusting thenormal spacing between said actuator and switch comprising a cam carriedby said shaft and movable axially thereof, resilient means for urgingsaid actuator into mechanical contact with said cam, and means operableduring rotation of said shaft for axially moving said cam.

8. Power transmitting mechanism comprising a pulley provided with aninternal abutment and freely mounted on a shaft for limited angularmovement with respect thereto, said shaft being provided with anabutment flied thereto within said pulley, and a compression springretained between said abutments, said spring being of such stiflness asto transmit the normal load torque of saidmechanism and to yield whensaid mechanism is subjected ,to higher than normal torque, an electricalswitch carried by said pulley and provided with an actuator, and acooperating abutment carried by said shaft in position to contactsaidactuator to close said switch upon relative angular movement of saidpulley and said shaft, said cooperating abutment comprising an elementmounted for angular adjustment relative to said shaft for adjusting thenormal spacing between said actuator and said cooperating abutment.

9. Power transmitting mechanism comprising a pulley provided with aninternal abutment and freely mounted on a shaft for limited angularmovement with respect thereto, said shaft being provided with anabutment fixed thereto within said pulley, and a compression springretained between said abutments, said spring being of such stillness asto transmit the normal load torque of said mechanism and to yield whensaid mechanism is subjected to higher than normal torque, an electricalswitch carried by said pulley and provided with an actuator, acooperating abutment carried by said shaft in position to contact saidactuator to close said switch upon relaing between said actuator andsaid cooperating abutment, and means operable during operative rotationof said power transmitting means for adjusting said element. 4

zoom J. o'rro.

